SURGICAL PEARLS

Exploring the Suprachoroidal Space
(Part 1 of 2 in a series)

Steps to proper transconjunctival drainage of choroidal detachment

BY FLAVIO REZENDE, MD, PhD

Several techniques have been described for drainage of choroidal detachment (CD), with or without the aid of micro-incision vitrectomy surgery (MIVS). The technique described below may offer one of the safest and least complicated methods.

DRAINING A CHOROIDAL DETACHMENT

Although I prefer to use 25g trocars to drain serous and 23g trocars to drain hemorrhagic CD, they both work in these situations.

Step 1. Place an infusion line (at 60 mmHg) in the anterior chamber (AC). If the chamber is flat, viscoelastic injection can be used to re-form the AC prior to infusion cannula insertion. Note that if you place the infusion line in the sulcus/pars plicata/pars plana, the trocar blade that is required to place the cannula prior to the infusion line placement may hit the choroid or retina, which could cause bleeding or tears. In addition, the infusion line itself could end up in the suprachoroidal space, potentially contributing to worsening of the choroidal detachment.

Step 2. Place transconjunctival sclerotomy 7 mm from the limbus at the most detached quadrant (drainage location should be determined 1-2 days pre-operatively or intra-operatively using B-scan ultrasonography).

Ensure that CD height is at least 5 mm. This is the most difficult step because the trocar should be introduced as flatly as possible to the scleral plane to avoid inadvertent choroidal damage (Figure 1). The eye must be well stabilized to avoid globe rotation. Non-toothed tying forceps (McPherson’s style) can be used to grasp the conjunctiva and Tenon’s capsule together for increased stability. Even with the eye “pressurized” by the infusion line at high infusion pressure, it is much harder to create a sclerotomy when the choroid is detached. It is critical not to change the angle of entry even if penetrating the eye is challenging. Also, avoid too flat of an entry as it may lead to intra-scleral trocar placement instead of suprachoroidal. An angle of 20° is best to penetrate the scleral arc without harming any structures.

Figure 1. Surgical technique: A. A close-up look at the position of the trocar being inserted into the suprachoroidal space. Note the tangential angle of the trocar in relation to the sclera and away from the choroid and retina. B-E. After placing the anterior chamber infusion, the choroidal fluid/hemorrhage drains spontaneously through the cannulas without the need of pars plana vitrectomy or any other adjuncts/instruments.

ADDITIONAL TIPS

›› Always monitor the AC infusion line, as it may pop out during sclerotomy placement.

›› It’s preferable to use non-valved cannulas. If the valve can’t be removed, it can be maintained open with any forceps.

›› Typically, in serous CD, one drainage site is sufficient to drain most of the fluid. In hemorrhagic CD, more than one drainage site may be needed. After draining one site, examine the fundus with indirect ophthalmoscopy to see how much has been drained.

›› The goal of draining CD is not to resolve it completely, but to solve severe hypotony, kissing choroidals, and flat AC. Some residual choroidal fluid may be left behind.

›› In hemorrhagic CD, if possible, it’s always best to wait for blood liquefaction to occur (typically a 10-14 day period) while monitoring with B-scan.

›› “Dry tap” may occur. If in hemorrhagic CD, it may represent a clot blocking the cannula. Turning the cannula from side to side or a gentle scleral depression with a cotton swab may unblock the cannula and allow drainage. Ultimately, placing your vitrector inside the cannula on cutting mode can solve the problem. “Dry tap” in serous CD may indicate intra-scleral cannula position; or that the cannula is too anterior and is blocked by choroid, retina or vitreous (if so, sclerotomy placement at 7 mm from limbus is advised).

›› Avoid the 3 and 9 o’clock meridians to spare the ciliary nerve from possible trauma. If possible, it is always preferable to drain the infero-temporal quadrant first.

CONCLUSION

In most instances, vitrectomy isn’t necessary with this technique. If concomitant pathology is present, delaying vitrectomy is recommended if at all possible. If vitrectomy is indicated, try to avoid air-fluid exchange because CD often recurs during this step and may push fluid posteriorly, endangering the macula. NRP

REFERENCES

Editor’s note:

Stay tuned for an interesting video I will present this August during ASRS 2014 in San Diego. The video will focus on Exploring the Suprachoroidal Space… A trip to the previously “unknown”…

Dr. Rezende is chief of the retina division and an associate professor in the Department of Ophthalmology at the University of Montreal, where vitreoretinal he also heads the fellowship program.